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libbpf: add tracepoint attach API

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Allow attaching BPF programs to kernel tracepoint BPF hooks specified by
category and name.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Andrii Nakryiko 2019-07-01 16:58:59 -07:00 committed by Daniel Borkmann
parent b265002747
commit f6de59c17f
3 changed files with 84 additions and 0 deletions
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79
tools/lib/bpf/libbpf.c
View File

@ -4190,6 +4190,85 @@ struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog,
return link;
}
static int determine_tracepoint_id(const char *tp_category,
const char *tp_name)
{
char file[PATH_MAX];
int ret;
ret = snprintf(file, sizeof(file),
"/sys/kernel/debug/tracing/events/%s/%s/id",
tp_category, tp_name);
if (ret < 0)
return -errno;
if (ret >= sizeof(file)) {
pr_debug("tracepoint %s/%s path is too long\n",
tp_category, tp_name);
return -E2BIG;
}
return parse_uint_from_file(file, "%d\n");
}
static int perf_event_open_tracepoint(const char *tp_category,
const char *tp_name)
{
struct perf_event_attr attr = {};
char errmsg[STRERR_BUFSIZE];
int tp_id, pfd, err;
tp_id = determine_tracepoint_id(tp_category, tp_name);
if (tp_id < 0) {
pr_warning("failed to determine tracepoint '%s/%s' perf event ID: %s\n",
tp_category, tp_name,
libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));
return tp_id;
}
attr.type = PERF_TYPE_TRACEPOINT;
attr.size = sizeof(attr);
attr.config = tp_id;
pfd = syscall(__NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,
-1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
if (pfd < 0) {
err = -errno;
pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n",
tp_category, tp_name,
libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
return err;
}
return pfd;
}
struct bpf_link *bpf_program__attach_tracepoint(struct bpf_program *prog,
const char *tp_category,
const char *tp_name)
{
char errmsg[STRERR_BUFSIZE];
struct bpf_link *link;
int pfd, err;
pfd = perf_event_open_tracepoint(tp_category, tp_name);
if (pfd < 0) {
pr_warning("program '%s': failed to create tracepoint '%s/%s' perf event: %s\n",
bpf_program__title(prog, false),
tp_category, tp_name,
libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
return ERR_PTR(pfd);
}
link = bpf_program__attach_perf_event(prog, pfd);
if (IS_ERR(link)) {
close(pfd);
err = PTR_ERR(link);
pr_warning("program '%s': failed to attach to tracepoint '%s/%s': %s\n",
bpf_program__title(prog, false),
tp_category, tp_name,
libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
return link;
}
return link;
}
enum bpf_perf_event_ret
bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
void **copy_mem, size_t *copy_size,

4
tools/lib/bpf/libbpf.h
View File

@ -178,6 +178,10 @@ LIBBPF_API struct bpf_link *
bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
pid_t pid, const char *binary_path,
size_t func_offset);
LIBBPF_API struct bpf_link *
bpf_program__attach_tracepoint(struct bpf_program *prog,
const char *tp_category,
const char *tp_name);
struct bpf_insn;

1
tools/lib/bpf/libbpf.map
View File

@ -171,6 +171,7 @@ LIBBPF_0.0.4 {
bpf_object__load_xattr;
bpf_program__attach_kprobe;
bpf_program__attach_perf_event;
bpf_program__attach_tracepoint;
bpf_program__attach_uprobe;
btf_dump__dump_type;
btf_dump__free;